You can send the parcel 1st class, the term standard parcels is misleading as parcels can also be sent 1st or 2nd class depending on weight. Sometimes particularly if a parcel isn't very heavy it is cheaper to send it 1st class rather than standard parcels. If your parcel weighs under 750g then it will be £2.70 to post.

I'm getting confused here. I have a small box to post, it's 0.5kg, just small shoe box size. Royal Mail site and are saying it'll be over £5 if I send it standard parcels (economy service apparently) but if I send it first class then it'll be £2.70 ish?

Can someone explain? I quoted £3 for postage, so don't want to send standard parcels if I can avoid it. Is there some reason I shouldn't send 1st class? (I did have parcels selected when I was working out the price, so the quote isn't for large letter or something)